The only reason the sock has its own section is to keep it upright...lol
The way I have it seems to be working pretty well, I can give the refugium a variable amount of water flow, instead of a fixed full water flow. There are lots of discussions about how much flow you should be cycling through your tank, with lots of people experimenting with more than 10% flow. I am pushing 15% flow at the moment, and plan on experimenting with different amounts, I think 15% is way to much for flow through a refugium, but thats just what I have concluded from reading and posting.